This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPP third generation partnership project
AGCH access grant channel
BCCH broadcast control channel
BSC base station controller
BTS base transceiver station
CCCH common control channel
DL downlink (BS to MS)
EDGE enhanced data rates for GSM evolution
eNB evolved node B
GERAN GSM EDGE radio access network
GSM global system for mobile communication
LTE long term evolution of UTRAN (E-UTRAN)
LTE-A LTE advanced
MBMS multimedia broadcast multicast service
MPRACH MBMS packet random access channel
MS mobile station
MTC machine type communications
PBCCH packet BCCH
PRACH physical random access channel, packet random access channel
RACH random access channel
RADCH random access data channel
RADCK random access data channel acknowledge
TBF temporary block flow
UE user equipment
UL uplink (MS to BS)
UTRAN universal terrestrial radio access network
Due to its increased importance studies are underway for network enhancements for machine type communications (MTC). The envisaged use cases for MTC devices are manifold: smart metering, e-health, fleet management, bridge monitoring, object and person tracking, theft detection and so forth. It is expected that in the next few years there will be, approximately, 20 MTC devices for each normal mobile phone. This implies that MTC traffic will consume a considerable amount of radio resources and may have the potential to degrade the performance of normal mobile phone traffic. By 2020 there are estimated to be 50 billion devices connected wirelessly to various networks.
A study item has been initiated at GERAN for MTC enhancements for GSM in Release 10. This issue has also been discussed in the standardization of MTC for LTE. The focus on these study items is to cover enhancements for applications requiring rather low data throughput, low cost, low power consumption and wide coverage. One example of such an application are smart meters, which would report status information and measurements of electricity, gas, heat, water, etc., to a central station that gathers this information for charging each user.
In at least some of the MTC applications it is expected that the service provider using the MTC devices, e.g., an electricity utility, would require small messages to be sent in a frequent manner. This could be required when there is the need for this information for controlling electricity grid parameters, e.g., in smart grids. These short and ‘instant’ messages are not expected to occur in existing networks (e.g., existing cellular-type networks). As a result, problems could arise due to the large signaling overhead that would be generated by the large number of small messages.
It has been shown that signaling channels may be a significant bottleneck when MTC applications start to be widely deployed in GSM networks (GP-100893 Bottleneck Capacity Comparison for MTC, Telefon AB LM Ericsson, ST-Ericsson, 3GPP GERAN#46). In some applications there could be a large number of messages created by MTC devices which could overload existing signaling channels and complicate the allocation of data resources. If one assumes that small messages are sent by the MTC devices the signaling overhead would be considerable when compared to the actual raw data being transmitted. This scenario implies the potential existence of an inappropriate and unbalanced usage of available wireless network resources.
A high volume of MTC messages will also degrade the user experience of human subscribers using web browsing and other non-real time services.
In the UL the normal access procedure in GSM is controlled by RACH parameters T and S, as shown in FIG. 1A. Once data traffic is generated in the MS it sends a RACH request after some random period between 0 and T−1. If no AGCH response is received, another request is sent after a random period between S and S+T−1. The retransmission is held until a maximum number of retransmissions M is attempted, or until a valid response in the AGCH is received. If the maximum number of retransmissions is attempted and no response in the AGCH is received the MS may start a cell-reselection procedure.
In LTE a similar procedure is performed as compared to the GSM procedure. In the first stage the MS sends to the eNB a message on PRACH (physical random access channel) which contains a preamble and a cyclic prefix as in FIG. 1(b). When the message is correctly decoded a PRACH response is sent from the eNB with a matching preamble, the UL resource and timing advance (TA) information. In a case wherein no response is received the MS attempts a new retransmission, and continues until a successful response is obtained in the DL.
In both of these current cellular technologies there is a limitation on the amount of data that can be transmitted during access bursts. A large guard period is needed for the burst formats for GSM and LTE since there is no information on the timing advance needed for the location of the MS before the access procedure. This is shown in FIG. 2B and FIG. 3 respectively.
For a MTC device that is not connected to a power main, e.g., an MTC device that is battery powered, a high number of access requests and several failed attempts can quickly consume the battery power.